Improving the impact resistance of molded articles enhances the industrial applicability of such molded articles significantly, not only by expanding the number of potential applications, but also by enabling the molded articles to be made with thinner walls or in larger sizes. As a result, numerous techniques have already been proposed for improving the impact resistance of molded articles.
Among these techniques, one technique which uses a resin material containing a combination of a rubber-like polymer and a hard resin to enhance the impact resistance of the molded article while retaining the inherent properties derived from the hard resin is already being used in industrial settings. Examples of this type of resin material include acrylonitrile-butadiene-styrene (ABS) resins, acrylonitrile-ethylene/α-olefin-styrene (AES) resins, polyorganosiloxane-acrylate-acrylonitrile-styrene (SAS) resins, acrylonitrile-styrene-acrylate (ASA) resins, and thermoplastic resin compositions prepared by adding one of these resin materials to a hard resin.
Examples of thermoplastic resin compositions that have been proposed which are capable of forming a molded article having improved impact resistance while retaining the properties derived from the hard resin include the following thermoplastic resin compositions.
(1) A thermoplastic resin composition obtained by adding an SAS resin to a methacrylate ester hard resin (Patent Document 1).
(2) A thermoplastic resin composition obtained by adding an SAS resin to a maleimide-based copolymer hard resin (Patent Document 2).
(3) A thermoplastic resin composition obtained by adding an AES resin to a methacrylate ester hard resin (Patent Document 3).
(4) A thermoplastic resin composition obtained by adding an AES resin to a maleimide-based copolymer hard resin (Patent Document 4).
(5) A thermoplastic resin composition obtained by adding an AES resin and an ASA resin to a methacrylate ester hard resin (Patent Document 5).
However, in the thermoplastic resin composition of (1), a large amount of the SAS resin must be added to improve the impact resistance of the molded article, and therefore in the resulting molded article, the surface hardness (scratch resistance), heat resistance and heat aging resistance derived from the methacrylate ester resin deteriorate markedly.
In the thermoplastic resin composition of (2), because a maleimide-acrylonitrile-styrene copolymer is used as the hard resin, the weather resistance and heat aging resistance of the molded article deteriorate markedly.
In the thermoplastic resin composition of (3), a large amount of the AES resin must be added to improve the impact resistance of the molded article, and therefore in the resulting molded article, the surface hardness (scratch resistance) derived from the methacrylate ester resin tends to deteriorate markedly. Further, if an attempt is made to improve the heat resistance of the this type of molded article, then the balance of properties deteriorates further and satisfactory performance cannot be maintained.
In the thermoplastic resin composition of (4), a large amount of an AES resin having a comparatively large particle size must be added to improve the impact resistance of the molded article, and therefore the coloration of the molded article tends to deteriorate.
In the thermoplastic resin composition of (5), an AES resin and an ASA resin are added to suppress any deterioration in the coloration of the molded article, but the impact resistance of the molded article is inferior to that obtained by adding only an AES resin.